The present invention relates to control valves and in particular, to an evaporative (EVAP) solenoid control valve having enhanced durability and noise reduction features.
It is known in the art of automotive fuel systems to use an evaporative (EVAP) solenoid valve assembly to control the flow of fuel vapor through passageways connecting a purge canister and an intake manifold. One such EVAP control valve assembly includes a solenoid assembly actuated in response to a pulse width modulated (PWM) signal generated by the vehicle""s central computer to induce a rubber-tipped plunger to move toward a metal stop, opening a passageway to the flow of vapor. When the solenoid is de-energized, the plunger is pushed back toward a valve seat by a pre-loaded spring situated between the stop and the plunger, causing the rubber-tip of the plunger to seal the passageway.
To reduce the noise caused by the impact of the plunger against the metal valve stop, EVAP control valve plungers have been designed to include a soft, rubber-like stop cushion at the interface with the valve stop. Repeated impact with the metal valve stop, however, may cause deterioration of the stop cushion which may, in turn, contribute to additional noise. Moreover, such cushions, generally injection molded onto a metal preform plunger body, may be formed with a dimple at or near the cushion-stop impact surface.
The present invention provides an improved evaporative control valve with enhanced durability and noise reduction features. In general, the control valve includes a valve body defining an inlet, a controlled outlet and a passageway therebetween. A valve stop and a valve seat are supported within the valve body in axial alignment with the controlled outlet. A plunger is reciprocably moveable between the valve stop and the valve seat to open and close the controlled outlet and further includes a central bore having an insert molded therein to define a stop-cushion at an end proximal the valve stop and a valve tip at an end proximal the valve seat. Connecting the stop cushion with the valve tip allows the cushion to be molded through the body of the plunger so that injection molding equipment interfaces with a non-impact surface of the insert (e.g. the side of the valve tip), and does not disturb the cushion-stop impact surface.
According to another aspect of the invention, the stop cushion may be dome-shaped to provide a greater quantity of material for enhanced impact absorption and to increase the size of the stop-impact surface. This results in less stress and wear on the assembly components.
Another aspect of the invention provides for a valve stop including a non-conducting surface, which may take the form of a plastic insert, that improves the path of the magnetic flux and reduces noise created by the impact of the plunger against the stop.
Yet another aspect of the invention includes placement of the spring within a plunger pocket formed in the end of the plunger proximal the valve stop to improve spring force distribution and plunger-to-valve seat alignment.
The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings and appended claims.